multivitamins are the most common dietary supplement in the u.s. a third of adults take them. doctors say taking multivitamins isn't the way to prevent heart disease. >> it's not a substitute for a well balanced diet or regular exercise. >> reporter: thompson says he will keep taking his multivitamin to make sure he gets the vitamins and minerals he needs. he says he eats right and gets plenty of exercise to stay healthy. edward lawrence for cbs news, los angeles. >> and last month the same group of researchers reported some benefits with multivitamins. men in the study had an 8% lower risk of cancer. >>> splitting the bill may be more of a pain than you think. a new study suggests the anxiety caused by even simple math problems can actually cause you physical pain. researchers at the university of chicago found people solving tough equations showed the same brain activity linked to the sensation of pain and that brain activity was greater for folks who admitted to having a fear of math. >>> lawrence, were you good at math? >> not bad. record-breaking numbers around the bay ar